PROJECT SUMMARY Bladder cancer (BC) is the sixth most common cancer in the U.S., has one of the highest recurrence rates of all solid cancers, and is the most expensive cancer to treat from diagnosis to death. There are significant unmet needs for biomarkers and molecular diagnostic tools to better inform decision making across all stages of BC. This includes prediction of treatment response in patients with non-muscle invasive (NMIBC) and muscle invasive bladder cancer (MIBC), as well as improving diagnostic yield in patients undergoing screening cystoscopy for hematuria. Our long-term goal is to improve outcomes for BC patients through the development and application of molecular biomarkers that facilitate personalized approaches to detection and treatment. Urine is an attractive source for development of BC diagnostics and we recently developed a novel strategy for detecting urine tumor DNA called urine tumor DNA Cancer Personalized Profiling by Deep Sequencing (uCAPP-Seq). Our preliminary data indicate that uCAPP-Seq has outstanding sensitivity and specificity for detection and surveillance of BC. In this project we will prospectively collect urine and other biospecimens from patients with or at risk for BC and will test the potential clinical utility of uCAPP-Seq in different clinical scenarios. We will also test if augmenting uCAPP-Seq with analysis of urinary RNA or DNA methylation further augments performance. Our central hypothesis is that uCAPP-Seq will enable monitoring of BC responses during and after treatment for NMIBC and MIBC. Furthermore, we hypothesize that combining analysis of urine DNA mutations, DNA methylation, and urine RNA will allow ultrasensitive and specific early detection of BC. We propose three specific aims: 1) To assess the value of urine tumor DNA for non-invasive response assessment and monitoring in patients with high risk NMIBC treated with bacillus Calmette-Gurin (BCG) immunotherapy; 2) To determine if urine tumor DNA analysis can predict pathologic complete responses to neoadjuvant chemotherapy in patients with MIBC; and 3) To develop a Bladder Cancer Interception Assay (BCIA) which integrates utDNA mutations and methylation with urinary RNA for ultra-sensitive detection of bladder cancer. Successful completion of the studies proposed here will serve as a foundation for incorporating our novel urine-based biomarkers into prospective clinical trials. We foresee that our approach will allow personalization of treatment strategies to improve outcomes for BC patients. Importnatly, our work will serve as proof-of- principle for an approach that could also be applied to other genitourinary cancer types.